Java is obviously a more advanced language than BASIC, with object-oriented features and all, but knowing the basic principles of programming puts you one step ahead of the game.
It is quite a different language but look up some tutorials and you should be fine! My first language was actually TI's implementation of basic on the TI 84 calculator. It's not my favorite language but it was easy enough to learn TI's implementation without tutorials by just seeing what did what. While SmileBASIC is quite a bit different it shouldn't be much harder to learn.
